We are considering installing a dieselstove in our sailboat, and search as I might, I have not been able to find any useful comparisons between types of stack caps (and how their efficiency might change with varying stack lengths). Because of the layout of our boat, the stack will be short--near the 4 foot minimum required by Dickinson--and will come through the cabin roof below the sweep of the boom. I am worried about wind bleeding down off the main and causing backdrafts. The two types of cap that seem the best-designed to deal with this problem are the "DP" or "draft prevention" style, a squat cylindrical shape with vents on the sides, and a conical style which claims to "always create an updraft with wind in any direction." I would love to hear other suggestions or further information on either of these.